Cigarette filters



United States Patent M 3,320,961 CIGARETTE FILTERS Ivor Wallace Hughes,Fareham, Henry George Horsewell,

Totton, and Donal Michael Carroll, Southampton, England, assiguors toBrown and Williamson Tobacco Corporation, Louisville, Ky., a corporationof Delaware No Drawing. Filed July 7, 1964, Ser. No. 380,929 Claimspriority, application Great Britain, July 22, 1963, 29,004/ 63 3 Claims.(Cl. 131-267) This invention concerns improvements relating to filtersfor tobacco smoke.

Filters for tobacco smoke are already known which removes theparticulate phase of the smoke by mechanical means. These filters,formed from filamentary or sheet material, have differing capacities forthe removal of specific components which it may be desired to remove,and may also adversely afi'ect the taste of the filtered smoke. A largeproportion of these components occurs, partially at least, in the formof vapours which cannot be removed by mechanical filtration, but only byabsorption or adsorption on a suitable surface, or by chemical reaction.

Of these substances, the more volatile acidic compounds may be thosewhich it is particularly desired to remove, An object of the presentinvention is to provide simply but eifective means whereby a substantialproportion of these acidic compounds can be removed from the smoke ofburning tobacco.

According to the invention, filamentary or sheet tobacco-smoke filtermaterial is treated with an alkaline sodium salt of orthophosphoricacid, i.e. the di-sodium salt or the tri-sodium salt.

The salt may be applied to the supporting material, constituting thebulk of the filter, as a solid in powder form by dusting or as a liquidin solution form by spraying, coating, dipping or the like. The amountof the salt added may be from 5% to 25% weight (calculated as anhydrousmaterial) of the weight of the supporting material) of the weight of thesupporting material, i.e. 5-25 gms. of anhydrous salt added to 100 gm.paper, but an addition of from to 20% is preferred.

Examples of ways of carrying out the invention will now be more fullydescribed:

Example 1 1 gm. of trisodium phosphate was dissolved in 47 mls. of waterand 4 mls. of this solution was evenly sprayed on to a strip ofopen-mesh creped wadding (such for example as that known as Myria paper)90 mm. wide and weighing approximately 0.8 gm. so as to give a finalconcentration, on a weight basis, of 10% of phosphate. The treated paperwas allowed to dry overnight at room temperature (20-25 C.) and was thenrolled by hand to form a rod which was 90 mm. long and of cigarettediameter. mm. lengths of the rod were attached as filters to cigarettesand the cigarettes were smoked by machine at l putt per minute, eachpuff being of 2 sec. duration and a volume of 35 mls. The smoke obtainedfrom the cigarettes was then analyzed in comparison with that fromcontrol cigarettes to which untreated filters had been at tached. Theuntreated filters, in this and the following examples, were preparedexactly as the treated filters,

3,320,961 Patented May 23, 1967 except that water was applied instead ofa solution of the sodium salt. The results of the analysis were asfollows:

Similar filter paper was treated exactly as in Example 1 except that itwas sprayed with 8 mls. of the trisodium phosphate solution, so as togive a final concentration of 20% by weight of the phosphate. Cigaretteswith treated and untreated filters were then smoked as previouslydescribed. Analysis of the smoke from the treated filters showed that60% of the acids had been retained.

Example 3 Similar filter paper was treated as in Example 1 except that asolution of disodium hydrogen phosphate was used. Cigarettes withtreated and untreated filters were then smoked as described previously.The results obtained are given below:

Percent of smoke Percent constituents retained NazHPOi Pressure drop byfilter on paper of 15 mm. tip

Acids Tar Nicotine Example 4 A continuous strip of 11 /2 inch wide openmesh creped wadding (such for example as Schweitzer paper) was passedunder a sponge roller and was roller coated with a solution of 2 kgs. oftrisodium phosphate in. 20 litres of Water. The rate of travel of thepaper was arranged so that the final concentration of phosphate on thepaper was 18% by weight. The paper was dried by hot air and formed intoa continuous filter rod, using conventional means. 15 mm. lengths of rodwere attached to cigarettes and smoked as in Example 1. The smokeanalysis results are compared below:

Cellulose acetate tow of total denier of 90,000 and denier per filamentof 5 was opened out and sprayed with a solution of trisodium phosphateso as to give a final concentration on the tow of approximately 10%.After drying, the tow was formed into filter rods. Sections of 15 mm.length were cut from the rods, attached to cigarettes and smoked asdescribed in Example 1. Analysis of the smoke from the treated filtersshowed that 57% of the acids were retained in comparison with only 33%when untreated filters were used.

As may be seen from the results, the addition of the diand tri-sodiumsalts of ortho-phosphoric acid to conventional filtering materials makesthese materials particularly effective in the removal of volatile acidsfrom tobacco smoke without adversely alfecting the removal of other 10constituents.

Little -or no adverse effect on the taste of the filtered smoke has beenobserved.

We claim:

1. A tobacco-smoke filter comprising fibrous tobaccosmoke filtermaterial treated with a water soluble alkaline sodium salt oforthophosphoric acid whereby a substantial proportion of acidiccompounds are removed from the smoke of burning tobacco withoutadversely affecting the organoleptic properties of the tobacco after thesmoke passes through the filter.

2. A tobacco-smoke filter as claimed in claim 1, wherein the said saltamounts to 10 to 20% by weight of the said filter material.

3. A tobacco smoke filter as claimed in claim 1 wherein the said saltamounts to 5% to 25% by weight of said filter material.

References Cited by the Examiner UNITED STATES PATENTS 2,940,456 6/1960Touey 131208 FOREIGN PATENTS 287,549 4/ 1953 Switzerland.

SAMUELKOREN, Primary Examiner.

D. J. DONOHUE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N003,320,961 May 23, 1967 Ivor Wallace Hughes et a1 a It is herebycertified that error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 1, line 37, after "25%" insert by lines 39 and 40, strike out "ofthe weight of the supporting materialy'o Signed and sealed this 28th dayof November 1967c (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

1. A TOBACCO-SMOKE FILTER COMPRISING FIBROUS TOBACCOSMOKE FILTERMATERIAL TREATED WITH A WATER SOLUBLE ALKALINE SODIUM SALT OFORTHOPHOSPHORIC ACID WHEREBY A SUBSTANTIAL PROPORTION OF ACIDICCOMPOUNDS ARE REMOVED FROM THE SMOKE OF BURNING TOBACCO WITHOUTADVERSELY AFFECTING THE ORGANOLEPTIC PROPERTIES OF THE TOBACCO AFTER THESMOKE PASSES THROUGH THE FILTER.